1. Field of the Invention
The present invention relates to a device for automatically detecting broadcasting signals and a method used by the device, and more particularly, to a device for automatically detecting broadcasting signals and a method used by the device for conveniently detecting the broadcasting system of broadcasting signals.
2. Description of the Related Art
Various broadcasting systems are used in different countries of the world according to territorial and cultural characteristics.
Examples of broadcasting systems include the NTSC system, the PAL system, and the SECAM system.
The Radio Corporation of America (RCA) developed color television, which was compatible with black and white television, and required a standard. Thus, the national television system committee (NTSC) adopted the NTSC system as the standard used in the United States in December 1953.
In addition, the PAL system was proposed by Walter Brach of Telefunken company and adopted as a standard in West Germany, Great Britain, The Netherlands, and Switzerland. The name of the PAL system originates from “Phase Alternation by Line.”
In addition, the SECAM system was proposed by Henri de France in 1957 and adopted as a standard in France, Russia, and East Germany. The name of the SECAM system originates from “sequential couleur's memories” which means sequentially memorizing color signals in each scan line.
Such broadcasting systems can be classified based on the number of scan lines, field rate, color sub-carrier frequency, and phase, as shown in Table 1.
TABLE 1NTSCNTSC4.43PALPAL60PAL-NPAL-MSECAMNumber of525525625525625525625scan linesField rate60605060506050Color Sub-3.584.434.434.433.583.58For = 4.40carrierFob = 4.25frequencyPhaseFixedFixedShiftShiftShiftShiftShift
Broadcasting systems vary from region to region and country to country, and thus, a device for receiving broadcasting signals are set to receive broadcasting signals corresponding to the region/country in which they are used.
In this case, when a device receives broadcasting signals of various broadcasting systems, an additional device for receiving the broadcasting signals of various broadcasting systems is required.
Accordingly, an apparatus for determining the type of broadcasting system and receiving corresponding broadcasting signals based on the determination result is proposed.
A conventional method of detecting a broadcasting system is shown in FIG. 1A. Referring to FIG. 1A, in operation S1, it is determined whether broadcasting signals received through a device for receiving broadcasting signals are in the SECAM system.
In this case, the order in which determinations are made for whether different broadcasting systems are received can be changed.
In other words, a determination of whether other broadcasting systems are received can be made prior to checking for the SECAM system.
On the other hand, the SECAM system may be determined using a register of the device for receiving broadcasting signals in which a predetermined value is set according to the broadcasting system.
If the received broadcasting signals are SECAM system signals, the received broadcasting signals are determined to be SECAM system signals in operation S2. If the received broadcasting signals are signals other than a SECAM system signal, a color sub-carrier frequency of the received broadcasting signals is determined in operation S3. In this case, the color sub-carrier frequency is first used in multi-step modulation and denotes a color carrier frequency used in modulating color signals in the NTSC system.
More specifically, after performing color signal modulation and sharing a brightness signal and a frequency spectrum, a final modulation is performed using a higher frequency. In this case, the carrier wave used in the final modulation is referred to as a main carrier wave.
If the color sub-carrier frequency is 4.43 MHz, in operation S4, it is determined whether the color format of the received broadcasting signals is in the PAL system in operation S5.
If the color format of the received broadcasting signals is in the PAL system, it is determined that the received broadcasting signals are PAL system signals in operation S6. Otherwise, in operation S7 the received broadcasting signals are determined to be NTSC system signals. In this case, the order of determining the color format of the received broadcasting signals can be changed.
If the color sub-carrier frequency is a frequency other than 4.43 MHz, e.g., 3.58 MHz, it is determined whether the received broadcasting signals are PAL-N system signals in operation S8.
If the received broadcasting signals are PAL-N system signals, it is determined whether the color format of the received broadcasting signals is in the PAL system in operation S9.
If the color format of the received broadcasting signals is in the PAL system, the received broadcasting signals are determined to be the PAL-N system signals in operation S10.
If it is determined that the received broadcasting signals are not in the PAL-N system, the following process described with reference to FIG. 1B is performed.
If the broadcasting signals are determined to be signals other than PAL-N system signals in operation S8, it is determined whether the received broadcasting signals are in the PAL-M system in operation S14.
If the received broadcasting signals are in the PAL-M system, it is determined whether the color format of the received broadcasting signals is in the PAL system in operation S15.
If the color format of the received broadcasting signals is in the PAL system, it is determined that the received broadcasting signals are in the PAL-M system in operation S16.
If the color format of the received broadcasting signals is not in the PAL system, a first basic clock frequency for detecting the color format is incremented by a predetermined value to produce a first clock frequency in operation S17, then the color signal of the received broadcasting signals is detected in operation S18.
When the color signal is detected, the broadcasting signals are determined to be PAL-N system signals in operation S19. Otherwise, the broadcasting signals are determined to be NTSC system signals in operation S20.
Thereafter, the first clock frequency is returned to the first basic clock frequency by decreasing the first clock by a predetermined value in operation S21.
On the other hand, when the broadcasting signals are not PAL-M system signals, the color signal of the received broadcasting signals is detected in operation S22, then the broadcasting signals are determined to be PAL-N system signals in operation S23.
If the color signal is not detected in the received broadcasting signals, a second basic clock for detecting the color signal is incremented by a predetermined value to produce a second clock frequency in operation S24.
Thereafter, it is determined whether the color format of the received broadcasting signals is in the PAL system in operation S25.
When the color format of the received broadcasting signals is in the PAL system, the received broadcasting signals are determined to be PAL-N system signals Otherwise, the received broadcasting signals are determined to be NTSC system signals in operation S26.
In addition, the second clock frequency is returned to the second basic clock frequency in operation S28.
The conventional method of detecting broadcasting signals detects the broadcasting systems of various broadcasting signals using broadcasting types, color formats, and color signals that are determined based on a predetermined bit value of a register, which is set according to the received broadcasting signals.
However, such a conventional method requires complicated processes for determining the broadcasting signals, thus a time for determining the broadcasting signals is increased.